The present invention relates to a speech synthesizer apparatus, and more particularly to a speech synthesizer apparatus having a memory storing information necessitated for speech synthesis in which information is selected and taken out of the memory and speech is synthesized on the basis of the taken-out information.
The field of application of a speech synthesizer apparatus is spreading more and more in recent years. Moreover, a number of kinds of speech synthesizing techniques have been heretofore published, and recently a speech synthesizer apparatus making use of a microcomputer has attracted the public eye and has begun to be used widely. Briefly speaking, a microcomputer is composed of a first memory for storing a plurality of groups of instructions (i.e. microinstructions) to be used for processing speech synthesis, a second memory for storing processed data and a central processing unit (CPU) for processing data on the basis of the instructions. This has been rapidly developed owing to the progress of the LSI technique, and it involves many advantages such as compactness, light weight, low cost, etc. Accordingly, synthesizing processing can be achieved simply and at a low cost with the microcomputer applied to the speech synthesizer. In such a case, normally the instructions for controlling speech synthesis are stored in the above-referred first memory, and synthesizing processing is effected by the above-referred CPU (also called "microprocessor"). Further, data processed for synthesis are stored in the above-referred second memory. It is to be noted that speech information could be stored either in the first memory or in the second memory. However, in the case where the necessary speech information is obtained by analyzing pronounced original speech and subsequently speech synthesis is effected on the basis of the obtained speech information, it is preferable to store the speech information in the second memory which is formed as a memory capable of writing and reading information (i.e. RAM: random access memory). On the other hand, in the case where speech synthesis is effected on the basis of preliminarily prepared speech information, it is preferable to have the speech information preliminarily stored in the first memory which is formed as a read-only memory (ROM) in which information is permanently stored. A speech signal obtained after completion of the synthesizing processing is normally subjected to digital-analog conversion and fed to a loud speaker via a filter and an amplifier to be pronounced from the loud speaker.
The above description has been made merely for explaining the simplest construction to practice a speech synthesizing technique and a data processing technique in combination, and as a matter of course, it is possible to combine, besides the microcomputer, a personal computer, minicomputer or large-scale computer having higher program processing capabilities with the speech synthesizing technique. It is to be noted that the present invention is not limited to the use of a microcomputer but is equally applicable to the case where a large-scale computer, a personal computer, or a mini-computer is employed.
The heretofore known or already practically used speech synthesizing techniques are generally classified into two types. One is a parameter synthesizing technique, in which parameters characterizing a speech signal are preliminarily extracted. Speech is synthesized by controlling multiplier circuits and filter circuits according to these parameters. As representative apparatuses of this type, there are known a linear predictive coding synthesizer apparatus and a formant synthesizer apparatus. The other type is a waveform synthesizing technique, in which waveform information such as an amplitude and a pitch sampled from a speech signal waveform at predetermined time intervals are preliminarily digitized. A speech signal is synthesized by sequentially combining each digital waveform information. As representative apparatuses of this type, there are known PCM (Pulse Coded Modulation), DPCM (Differential PCM) and ADPCM (Adaptive DPCM) synthesizer apparatuses, and a phoneme synthesizer apparatus which joins waveforms of primary phonemes forming the minimum units of speech successively to each other.
The present invention is characterized in processing mechanism for reading such parameter information or waveform information out of a memory and supplying it to a synthesizing processor. Therefore, more detailed description of the various types of synthesizing techniques as referred to above will be omitted here. However, it is one important merit of the present invention that the invention is equally applicable all of these synthesizing techniques. This is because in every speech synthesizing technique a digital processing technique such as a computer technique is involved and storing speech information (parameter information or waveform information) in a memory and reading information from a memory are essentially necessary processings.
In a heretofore known speech synthesizer apparatus, parameter information or waveform information of speech (hereinafter called simply "speech information") is written in a memory and the speech information is read out in accordance with address data fed from a CPU. For this purpose, the CPU includes an address data generating circuit which generates an address where a synthesized speech information is stored, in response to speech designating data from a speech request section such as a key board. That is, the same system as the address system of the conventional digital computer is employed. In other words, a program is preliminarily prepared so as to be able to synthesize desired speech, and addresses are generated according to the prepared program. In some commercially available speech synthesizers, designation of speech to be synthesized is effected by key operations. The procedure of processing is started by designating speech (anyone of phone, word and sentence) by means of a key input device. A key data is converted into a predetermined key code (key address), which is in turn converted into address data and applied to a memory. The applied address data serve as initial data, and a plurality of consecutive addresses are produced and successively applied to the memory. As a result, speech information stored at the designated memory locations is successively transferred to a CPU, and then synthesizing processing is commenced. However, the key input data and the address data of the memory had to be correlated in one-to-one correspondence. As viewed from the memory side, speech information had to be preliminarily stored at predetermined locations in the memory as correlated to the key data of the key input device.
Therefore, in the heretofore known speech synthesizer apparatus it was not allowed to disturb the relation between the key input device (or speech synthesizing program) and a memory for storing speech information, especially the basic rule of making the key data and the memory address coincident to each other. On the other hand, the quantity of speech information (the number of addresses to be preset in a memory) will be different in various manners depending upon a difference in a speech synthesizing system and a difference in speech itself. Accordingly, the respective leading addresses of the memory locations where respective first speech information of the respective information group of speech is to be stored cannot be preset at equal intervals or with the same address capacity. If it is assumed that the leading addresses of each speech were preset at equal intervals, the interval between the respective leading addresses must be selected so as to meet the speech having the largest quantity of information. Therefore, capacity of the memory becomes so large that it is not economical. Even from such a view point also, it will be understood that in the heretofore known speech synthesizer apparatus, the key data of a key input device must have one-to-one correspondence to the memory address of the speech information storage memory.
In the heretofore known speech synthesizer apparatus, as the key data is coincident with the memory address in the above-described manner, change of a memory was not allowed. More particularly, in the case where a presently used memory is to be changed to a memory of another speech, the leading address of the speech information stored in the replaced memory is different from that of the original memory. This is caused by the fact that the quantity of information is different depending upon the speech to be synthesized, as described previously. Accordingly, together with the replacement of a memory, the key data of the key board or the addressing system of the CPU also must be changed in the corresponding manner. Especially, in order to change the key data, the key input device itself must be replaced. Further, change of the address system of the CPU requires change of the hardware for generating a memory address depending on the key address and software for controlling the processing of the memory address. Therefore, it requires a lot of time and human labor as is well known. In addition, checking of a memory address generating program is also necessitated. As described above, if it is intended to replace a memory, then change of another portion of the apparatus becomes necessary, and hence, not only the apparatus becomes complex but also the operation becomes troublesome.
Furthermore, where a memory is to be newly added to the prior art synthesizers, the codes of the key data and addresses output from the CPU has to be newly preset at the time of adding the memory so as to correspond to the respective leading addresses in the additional memory. Therefore, modification of a hardware circuit (especially an interface between a CPU and a key input device) is necessitated, and hence there is a shortcoming that the speech synthesizer apparatus lacks adaptability to different applications.